[RFC PATCH v3 00/20] configure: create a python venv and ensure meson, sphinx

[John Snow]

GitLab CI: https://gitlab.com/jsnow/qemu/-/pipelines/846869409
           (All green, except Python self-tests, see below)

This patch series creates a mandatory python virtual environment
("venv") during configure time and uses it to ensure the availability of
meson and sphinx.

See https://www.qemu.org/2023/03/24/python/ for details. The summary is
that the goal of this series is to ensure that the `python` used to run
meson is the same `python` used to run Sphinx, tests, and any build-time
python scripting we have. As it stands, meson and sphinx (and their
extensions) *may* run in a different python environment than the one
configured and chosen by the user at configure/build time.

The effective change of this series is that QEMU will now
unconditionally create a venv at configure-time and will ensure that
meson (and sphinx, if docs are enabled) are available through that venv.

Some important points as a pre-emptive "FAQ":

- This venv is unconditionally created and lives at {build_dir}/pyvenv.

- The python interpreter used by this venv is always the one identified
  by configure. (Which in turn is always the one specified by --python
  or $PYTHON)

- *almost* all python scripts in qemu.git executed as part of the build
  system, meson, sphinx, avocado tests, vm tests or CI are always
  executed within this venv.

  (iotests are not yet integrated; I plan to tackle this separately as a
  follow-up in order to have a more tightly focused scope on that
  series.)

- It remains possible to build and test fully offline.
  (In most cases, you just need meson and sphinx from your distro's repo.)

- Distribution packaged 'meson' and 'sphinx' are still utilized whenever
  possible as the highest preference.

- Vendored versions of e.g. 'meson' are always preferred to PyPI
  versions for speed, repeatability and ensuring tarball builds work
  as-is offline.

  (Sphinx will not be vendored, just like it already isn't.)

- Missing dependencies, when possible, are fetched and installed
  on-demand automatically to make developer environments "just work".

- Works for Python 3.7 and up, on Fedora, OpenSuSE, Red Hat, CentOS,
  Alpine, Debian, Ubuntu, NetBSD, OpenBSD, and hopefully everywhere

- No new dependencies (...for most platforms. Debian and NetBSD get an
  asterisk.)

- The meson git submodule is unused after this series and can be removed.

For reviewers, here's how the series is broken up:

Patch 1 is a testing pre-req. Note that even with this patch,
'check-python-minreqs' and 'check-python-tox' CI jobs will both still
fail on origin/master because this series requires 3.7+, but
origin/master is currently still 3.6+.

- python: update pylint configuration

Patches 2-8 add the mkvenv script. The first patch checks in the barest
essentials, and each subsequent patch adds a workaround or feature one
at a time.

- python: add mkvenv.py
- mkvenv: add console script entry point generation
- mkvenv: Add better error message for missing pyexapt module
- mkvenv: generate console entry shims from inside the venv
- mkvenv: work around broken pip installations on Debian 10
- mkvenv: add nested venv workaround
- mkvenv: add ensure subcommand

Patches 9-11 modify our testing configuration to add new dependencies as
needed.

- tests/docker: add python3-venv dependency
- tests/vm: Configure netbsd to use Python 3.10
- tests/vm: add py310-expat to NetBSD

Patch 12 changes how we package release tarballs.

- scripts/make-release: download meson==0.61.5 .whl

Patches 13-16 wire mkvenv into configure and tests.

- configure: create a python venv unconditionally
- configure: use 'mkvenv ensure meson' to bootstrap meson
- configure: add --enable-pypi and --disable-pypi
- tests: Use configure-provided pyvenv for tests

Patches 17-20 delegate Sphinx bootstrapping to mkvenv. Some of these
changes could be folded earlier in the series (like the diagnose()
patch), but I'm keeping it separate for review for now.

- configure: move --enable-docs and --disable-docs back to configure
- mkvenv: add diagnose() method for ensure() failures
- configure: use --diagnose option with meson ensure
- configure: bootstrap sphinx with mkvenv

That's all for now, seeya!
--js

John Snow (20):
  python: update pylint configuration
  python: add mkvenv.py
  mkvenv: add console script entry point generation
  mkvenv: Add better error message for missing pyexpat module
  mkvenv: generate console entry shims from inside the venv
  mkvenv: work around broken pip installations on Debian 10
  mkvenv: add nested venv workaround
  mkvenv: add ensure subcommand
  tests/docker: add python3-venv dependency
  tests/vm: Configure netbsd to use Python 3.10
  tests/vm: add py310-expat to NetBSD
  scripts/make-release: download meson==0.61.5 .whl
  configure: create a python venv unconditionally
  configure: use 'mkvenv ensure meson' to bootstrap meson
  configure: add --enable-pypi and --disable-pypi
  tests: Use configure-provided pyvenv for tests
  configure: move --enable-docs and --disable-docs back to configure
  mkvenv: add diagnose() method for ensure() failures
  configure: use --diagnose option with meson ensure
  configure: bootstrap sphinx with mkvenv

 docs/devel/acpi-bits.rst                      |   6 +-
 docs/devel/testing.rst                        |  14 +-
 configure                                     | 139 +--
 .gitlab-ci.d/buildtest-template.yml           |   4 +-
 .gitlab-ci.d/buildtest.yml                    |   6 +-
 python/scripts/mkvenv.py                      | 871 ++++++++++++++++++
 python/setup.cfg                              |  10 +
 python/tests/flake8.sh                        |   1 +
 python/tests/isort.sh                         |   1 +
 python/tests/mypy.sh                          |   1 +
 python/tests/pylint.sh                        |   1 +
 .../org.centos/stream/8/x86_64/test-avocado   |   4 +-
 scripts/device-crash-test                     |   2 +-
 scripts/make-release                          |  11 +
 tests/Makefile.include                        |  10 +-
 .../dockerfiles/debian-all-test-cross.docker  |   3 +-
 .../dockerfiles/debian-hexagon-cross.docker   |   3 +-
 .../dockerfiles/debian-riscv64-cross.docker   |   3 +-
 .../dockerfiles/debian-tricore-cross.docker   |   3 +-
 tests/requirements.txt                        |   7 +-
 tests/vm/netbsd                               |   2 +
 21 files changed, 1016 insertions(+), 86 deletions(-)
 create mode 100644 python/scripts/mkvenv.py

-- 
2.39.2